Those illumination devices, concerning which an LED is applied in combination with a fiber-optic, in order to transport the light which is emitted by the LED to a location which is remote from the LED form the basis of the invention. Such illumination devices nowadays have a significant role to play in different technical fields. In this context for example, endoscopes are known, concerning which, for illumination purposes, light must be provided at the distal end of an elongate shank, wherein the LED is arranged at the proximal side of the shank either as a part of the endoscope or as part of a separate light source which is connectable to the endoscope.
If a large light yield is necessary at the end which is away from the LED, then accordingly large light fluxes must already be provided by the LED and coupled into the fiber optic. At the location of the coupling of light into the fiber-optic, this leads to a comparatively high thermal loading which can be explained by the fact that also those light beams which are emitted by the LED and have a comparatively large angle to the optical axis of the fiber-optic or to the optical axis of its fibers also reach the fiber-optic and due to the comparatively small numeric aperture of the fiber-optic or its fibers cannot be transmitted through the fiber-optic and instead of this are absorbed and converted into heat. In the most unfavorable case, this thermal loading can lead to a damaging of the fiber-optic.